A large aquatic animal, perhaps the extinct dinosaur, plesiosaurus, the exact meaning is unknown. Some think this to be a crocodile but from the description in Job 41:1-41:34 this is patently absurd. It appears to be a large fire breathing animal of some sort. Just as the bomardier beetle has an explosion producing mechanism, so the great sea dragon may have an explosive producing mechanism to enable it to be a real fire breathing dragon.